The following settings are supported in Visual MODFLOW Flex for the LAK package and facilitate the internal flow balance for the LAK package:
THETA: variable to specify an explicit (THETA=0.0), semi-implicit (0.0<THETA<1.0), or fully implicit (THETA=1.0) solution for lake stages
MSSITR: Maximum number of iterations for steady-state solution
SSCNCR: Convergence criterion for equilibrium lake stage solution by Newton's method.
The lake package has a known issue for steady-state simulations - the initial lake level specific is held constant for the simulation period and will not reach equilibrium with the heads in the surrounding hydrogeologic unit(s). The recommended action to determine the equilibrium lake-level is to simulate a transient run with sufficient duration to estimate the steady-state levels as input to a steady-state simulation.